landscape patter.pdfLABName: Section: Date: Exercise K: Landscape pattern PURPOSE: The purpose of this laboratory exercise is to review the concepts of species distribution and abundance. Much of ecological research is concerned with determining the environmental factors (abiotic) and species interactions (biotic factors) that explain the distributions of both individual species and assemblages of species (communities). KEY TERMS AND CONCEPTS: *Hint: Be able to define and compare-contrast each of these terms. Community Species Landscape Dispersion pattern Biosphere Ecosystem Part I. Ecology Ecology is the science of the relationships between organisms and their environment. Ecologists seek to understand order in nature by describing patterns and connections among organisms and between living things and the physical environment. Landscape ecologists are concerned with studying relationships between spatial pattern and ecological processes. Ecologists may be concerned with populations, groups of individuals of the same species that live in the same geographic region, communities, groups'of'interacting'species'occupying'the'same'area,'or'entire'ecosystems,'groups'of'interacting'species'and'the'abiotic'environment.' Fill in the blank: 1. The interactions between the organisms of a community and the physical factors of their environment is termed a __________________________. 2. All of Earth's water, land, and atmosphere within which life exists is known as the __________________________. 3. The fish, java ferns, snails, bamboo shrimp, and bacteria in my aquarium represent a __________________________.Part 2: Dispersion Pattern The spatial distribution of at any particular moment of a population is referred to as the dispersion pattern. Landscape ecologists are often interested in quantifying the spatial pattern of species across a landscape because it is an important driver of many ecological processes. There are three common population dispersion patterns, regular, random and clumped (Figure 1). Figure 1: Three common population dispersion patterns Truly random distribution are uncommon in nature since organisms tend to interact with both their environment and nearby organisms. Regular patterns are often seen in response to dispersed resources (e.g. telephone poles used as perching sites for birds) or through behavioral interactions (birds on a wire; or penguins in a rookery). Clumped distributions are most common and may be due to social behavior or habitat structure. To calculate the dispersion pattern a study area is divided into quadrats. The number of individuals in each quadrat are then counted and the average number of organisms per quadrat and the variance among quadrats is calculated. Variance is a measure of the amount of divergence about the average. A sample with widely fluctuating differences in the number of plants in each quadrat will have a large variance while one with a homogeneous data set will have a low variance. Low variance = Regular dispersion pattern (there is little variation between quadrats) High variance = Clumped dispersion pattern (there is high variation between Measuring Spatial Distribution Much of the research in ecology is ultimately tied to the problems of species distributions and abundance. In some cases, only a single species is of interest. Many of the earlier investigators were content to quantify population parameters for their favorite species in a variety of habitats. Recent research is more often concerned with assemblages of species (e.g. description at the community level). This research attempts to determine the environmental factors (abiotic factors) and species interactions (biotic factors) that may explain the observed patterns Figure 1 Dispersion patterns are described as regular, random, or clumped (Figure 1). Truly random distribution are uncommon in nature since organisms tend to interact with both their environment and nearby organisms (con- or heterospecific). Regular patterns are often seen in response to dispersed resources (such as telephone poles used as perching sites for birds) or through behavioral interactions (birds on a wire; or penguins in a rookery). Clumped distributions are most commonly seen (paper birch) and may be due to social behavior or habitat structure (for example, paper birch is found near water). To calculate the dispersion pattern the study area is divided into quadrats. The number of individuals in each quadrat are then counted and the mean number of organisms per quadrat and the variance among quadrats is calculated. Variance (abbreviated "s2") is a measure of the amount of divergence about the average (or mean; abbreviated " "). A sample with widely fluctuating differences in the number of plants in each quadrat will have a large variance while one with a homogeneous data set will have a low variance. If there is little variation from one quadrat to another (more or less the same number of organisms in each plot) then the organisms are said to have a "regular" or "dispersed" distribution and the variance to mean ratio (s2: ) will be less than 1.0. If many of the plots arequadrats) Variance:Mean ~ 1 = Random dispersion pattern Pooling data can provide additional information about landscape pattern (Figure 2). In Figure 2A, we see that there is dispersion pattern is clumped. However by aggregating the data, we see that the clumps themselves are clumped. Figure 2: Aggregation of quadrat data by 4 quadrats. Laboratory Procedure: In this lab, we will be looking at vegetation patterns in Chataqua Park. Using the gridded Google Earth image (page 6), you objective is to quantify the dispersion pattern of ponderosa pine. In this image, we will assume all green trees are ponderosa pine. Instead of counting the number of trees in each quadrat we will estimate the percentage cover of tree in each quadrat. Download the spreadsheet from the class website. For each quadrat in the image (labeled with rows 1-10 and columns A-N), estimate the percentage cover of ponderosa pine. Enter the percent cover in the corresponding cell of the spreadsheet. Do NOT enter data in any other portion of the spreadsheet. Excel will automatically calculate the average, mean and variance to mean ratio. Our handy dandy Excel spreadsheet will not only calculated the mean, variance and mean to variance ratio for the original data (yellow), but also horizontally Excel will